1. Field of the Invention
The present invention relates to a liquid crystal display panel and a fabricating method thereof, and specifically to a blue phase liquid crystal display panel and a fabricating method thereof.
2. Description of Related Art
In 1888, Friedrich Reinitzer placed cholesteric benzoate in a polarizing microscope and observed that the cholesteric benzoate renders different colors (blue violet and blue) in an isotropic phase and in a cholesteric phase, and a phenomenon of color change between the isotropic phase and the cholesteric phase merely exists in a small temperature range (the temperature range of about only 1° C.). In 1970, many scientists used methods such as volumetric analysis and high-resolution differential scanning calorimetry to verify that the phenomenon is a new thermodynamically stable phase, and called it a blue phase.
The blue phase exists as three different phases, and the three phases are referred to as BP I, BP II and BP III. BP III exists in the highest temperature among the three phases, and BP III is referred to as a “fog phase” in literature. Compared with the cubic structure of BP I and BP II, BP III is amorphous. Observed in the polarizing microscope, BP III is generally a blurred image without any structure, and therefore BP III is difficult to be observed in the polarizing microscope.
On the other hand, it has been verified in the structure of BP I and BP II that a basic unit forming BP I and BP II is double twist cylinders (DTC), and such an arrangement has the smallest free energy. Besides, the double twist cylinders are perpendicular to each other spatially, and such an arrangement leads to lattice defects, and is taken as a pre-transitional phenomenon from a liquid crystal phase to the cholesteric phase. Therefore, blue phases are classified as frustrated phases. Based on Bragg scattering, Kossel diffraction diagram, optical texture, crystal growth, and other experimental researches, it is discovered that BP II has a simple cubic (SC) structure (see Mol. Cryst. Liq. Cryst., Vol. 465, pp. 283-288, 2007), and BP I has a body-centered cubic (BCC) structure. Different from other liquid crystal phases such as nematic phase, smectic phase and isotropic phase, BP I and BP II generally display multiple color patterns of a platelet texture when observed in the polarizing microscope (see J.A.C.S, 2008, 130, 6326 Kikuchi et. al.), and this is due to the Bragg reflection caused by a lattice period in a wavelength range of visible light.
Common liquid crystal is optically anisotropic, but the blue phase is optically isotropic. In other words, the blue phase has a very low or even no birefringence.
Since the lattice period of the blue phase is a function of the wavelength range of visible light, the selective “Bragg reflection” is generated. Such a feature makes the blue phase capable of being applied to fast light modulators. However, no matter in theoretical prediction or experimental observation, a blue phase liquid crystal merely appears in a molecular material with high purity and high optical activity, and therefore the blue phase liquid crystal merely exists within a small temperature range (the temperature range of less than 2° C). Thus, the blue phase liquid crystal is generally discussed merely in the academia, but receives less attention in the field of real applications.
In the last decade, to make a display quality of a liquid crystal display panel surpass the display quality of cathode-ray tubes, the blue phase featuring a fast response again becomes a focus of the academia and the industry. To meet application demands, the blue phase liquid crystal has to be equipped with a wide range of temperature for application, and therefore different technological developments have been proposed successively. For example, a feature of stability of macromolecule (i.e. formation of polymer network) is utilized to generate the blue phase that can exist within a wide range of temperature (see Nature materials, 2002, 1, 64). Besides, in 2002, Kikuchi et al. added a small amount of monomers and photoresist agents into the blue phase liquid crystal, and irradiated the blue phase liquid crystal within the blue phase temperature range to generate a stable blue phase with a gel-like structure, and the blue phase existing within a temperature range of about 60° C. is thus successfully generated.
Although the blue phase liquid crystal has the advantages of fast response time and optical isotropy, it has the disadvantage of relatively high driving voltage, which can reach up to as 55 volts. From the viewpoint of mass production, the high driving voltage of the blue phase liquid crystal is one of the problems demanding solutions.